Molecular liquid TiCl4 and VCl4: Two substances, one structure?

Synchrotron X-ray diffraction measurements have been conducted on liquid phosphorus trichloride, tribromide and triiodide. Molecular Dynamics simulations for these molecular liquids were performed with a dual purpose: (1) to establish whether existing intermolecular potential functions can provide a picture that is consistent with diffraction data; (2) to generate reliable starting configurations for subsequent Reverse Monte Carlo modelling. Structural models (i.e., sets of coordinates of thousands of atoms) that were fully consistent with experimental diffraction information, within errors, have been prepared by means of the Reverse Monte Carlo method.Comparison with reference systems, generated by hard sphere-like Monte Carlo simulations, was also carried out to demonstrate the extent to which simple space filling effects determine the structure of the liquids (and thus, also estimating the information content of measured data). Total scattering structure factors, partial radial distribution functions and orientational correlations as a function of distances between the molecular centres have been calculated from the models. In general, more or less antiparallel arrangements of the primary molecular axes that are found to be the most favourable orientation of two neighbouring molecules. In liquid PBr 3 electrostatic interactions seem to play a more important role in determining intermolecular correlations than in the other two liquids; molecular arrangements in both PCl 3 and PI 3 are largely driven by steric effects.

Section: Introductionmentioning

confidence: 99%

The structure of PX3 (X = Cl, Br, I) molecular liquids from X-ray diffraction, molecular dynamics simulations, and reverse Monte Carlo modeling

Pothoczki

Temleitner

Pusztai

2014

“…2 As this methodology is not limited to this phase and/or compound, it has also been applied to investigate the similarities and differences between the liquid and plastic phases for both carbon tetrachloride and neopentane 3 and to the gas-liquid coexistence line for carbon tetrachloride; 4 recently, Pusztai et al applied this methodology to tin iodide 5 and several chlorinated compounds. 2,6 In order to complete the program outlined in Ref. 1, this work is devoted to an old question, namely, the possible existence of a common orientational order for liquids composed of tetrahedral molecules.…”

Section: Introductionmentioning

confidence: 99%

“…1, this work is devoted to an old question, namely, the possible existence of a common orientational order for liquids composed of tetrahedral molecules. 2,[6][7][8][9][10][11][12][13][14][15][16][17][18][19] In fact, up to now the discussion has been mainly circumscribed to the liquid tetrachlorides, 2,6,[8][9][10][12][13][14][15][16][17][18][19] and as it was the case for the nature and range of orientational correlations in carbon tetrachloride, no agreement seems to exist on this issue; while some authors have rejected the existence of a common orientational order, 12,13 others have supported it. 14,19 The most recent contribution is the study by Pothoczki and Pusztai 6 in which they apply the aforementioned classification method 1 to a comparison of the liquid phases of TiCl 4 and VCl 4 , concluding that their structural features are nearly indistinguishable.…”

Section: Introductionmentioning

confidence: 99%

Is there a common orientational order for the liquid phase of tetrahedral molecules?

Rey

2009

The title question is addressed with molecular dynamics simulations for a broad set of molecules: methane (CH4), neopentane (C(CH3)4), carbon tetrafluoride (CF4), carbon tetrachloride (CCl4), silicon tetrachloride (SiCl4), vanadium tetrachloride (VCl4), tin tetrachloride (SnCl4), carbon tetrabromide (CBr4), and tin tetraiodide (SnI4). In all cases the sequence of most populated relative orientations, for increasing distances, is found to be identical: The closest distances correspond to face-to-face followed by a dominant role of edge-to-face, while for larger distances the main configuration is edge-to-edge. The corner-to-face configuration plays an almost negligible role. The range of orientational order is also similar, with remnants of orientational correlation discernible up to the fourth solvation shell. The equivalence does not only hold in the qualitative terms just stated but is also quantitative to a large extent once the center-center distance is properly scaled.

“…In short, the initial models contained 2000 randomly oriented, flexible molecules ͑10 000 atoms͒ in cu-a͒ Author to whom correspondence should be addressed. 6,9,16,17 Further details of diffraction measurements and RMC simulations can be found in Ref. b͒ bic boxes with periodic boundary conditions, and were defined only by the appropriate density and molecular geometry.…”

Section: A Rmc Modelingmentioning

confidence: 99%

Extended orientational correlation study for molecular liquids containing distorted tetrahedral molecules: Application to methylene halides

Pothoczki

Temleitner

Pusztai

2010

The method of Rey [Rey, J. Chem. Phys. 126, 164506 (2007)] for describing how molecules orient toward each other in systems with perfect tetrahedral molecules is extended to the case of distorted tetrahedral molecules of c(2v) symmetry by means of introducing 28 subgroups. Additionally, the original analysis developed for perfect tetrahedral molecules, based on six groups, is adapted for molecules with imperfect tetrahedral shape. Deriving orientational correlation functions have been complemented with detailed analyses of dipole-dipole correlations. This way, (up to now) the most complete structure determination can be carried out for such molecular systems. In the present work, these calculations have been applied for particle configurations resulting from reverse Monte Carlo computer modeling. These particle arrangements are fully consistent with structure factors from neutron and x-ray diffraction measurements. Here we present a complex structural study for methylene halide (chloride, bromide, and iodide) molecular liquids, as possibly the best representative examples. It has been found that the most frequent orientations of molecules are of the 2:2 type over the entire distance range in these liquids. Focusing on the short range orientation, neighboring molecules turn toward each other with there "H,Y"-"H,Y" (Y: Cl, Br, I) edges, apart from CH(2)Cl(2) where the H,H-H,Cl arrangement is the most frequent. In general, the structure of methylene chloride appears to be different from the structure of the other two liquids.